Due to increasing demands for reduced carbon dioxide emissions, internal combustion engines are increasingly optimized with respect to fuel consumption. However, conventional internal combustion engines may not be optimally operated in operating points having high load with respect to consumption, since the operation is limited due to a knocking tendency and high exhaust gas temperatures. One potential measure for reducing the knocking tendency and for lowering the exhaust gas temperatures is the injection of water. In this case, separate water injection systems are normally present to enable the injection of water. Thus, for example, a water injection system for an internal combustion engine having an exhaust gas recirculation system is described in PCT App. No. WO 2014/080266 A1, in which the water is injected into the mass flow of the exhaust gas recirculation.
The pump used to convey the water is switched off between the operating points in which the water injection system is activated. This means that the water in the injectors and in the lines of the water injection system is standing. Because of the high temperatures of the parts of the internal combustion engine close to the water injection system, the standing water may heat up and possibly evaporate. This effect is intensified when driving at high elevations, where the air pressure is lower. The formation of vapor may result in functional impairments when restarting the water injection system, since the system pressure may be only slowly built up as a result of the vapor. This delays the operational readiness of the water injection system. This delayed operational readiness may result in temperature peaks in the exhaust gas as well as in incidences of knocking in the combustion during sudden load variations.